1. Field of the Invention
The present invention relates to a thermal roll, and a drying apparatus and method. More particularly, the present invention relates to a thermal roll, and a drying apparatus and method, in which distortion of web to be heated or dried can be prevented even when a great difference lies in the temperature between the web and the thermal roll.
2. Description Related to the Prior Art
A presensitized (PS) plate is produced by use of aluminum web in a continuous shape. On the aluminum web, at least one first surface is finished according to graining. The first surface is coated with liquid material that is printing plate producing layer forming solution, and includes photosensitive resin or thermosensitive resin.
In order to heat and dry the aluminum web coated with the printing plate producing layer forming solution, drying with fluid medium, such as hot gas, is generally used.
However, the drying with gas has serious problems in that a manufacturing system requires an excessively large size, because of very low heat transfer efficiency for transfer of heat to the aluminum web. Load in the drying is considerably high if the printing plate producing layer forming solution requires drying in a drying process for the aluminum web after being coated.
Various methods are known in the prior art to prevent excessive enlargement of the manufacturing system in view of the drying operation. For example, nozzles for blowing the hot gas at a high flow rate are used. Also, two paths for the hot gas are disposed for blowing two sides of the aluminum web with the hot gas.
However, the above-mentioned methods cannot be used in an initial step of the drying, because blowing the coated surface being still wet at a high flow rate of the hot gas is inappropriate, and causes nonuniformity in the condition of the coated surface. Should the flow rate of the hot gas be set remarkably higher, the heat transfer efficiency cannot be increased. The coated surface cannot be dried effectively.
It is possible to raise the heat transfer efficiency if thermal rolls are used according to a heating method of heat transfer. However, problems arise in occurrence of wrinkles, scratches, folds or other damages. The use of the thermal rolls has been effective only in a later half of the drying process in order to raise the temperature of the aluminum web by several degrees centigrade (° C.).
JP-A 9-066259, specifically pages 2 and 3 and FIG. 1, discloses an additional drying device. Also, there is conception of structurally simplifying the manufacturing system. However, it is difficult or impossible instantaneously to change the temperature of the hot gas. A change in the temperature condition of the aluminum web requires much time. This is a serious problem specially if a characteristic of the aluminum web, for example a width, thickness, web substance or the like, is altered within the uninterrupted web traveling through the manufacturing system for industrial requirement or for any reason. It is conceivable to stop or slow down the aluminum web in a temporary manner. However, such conceptions will cause waste of time in this step included in all the process of the manufacture.